WO2020190192A1

WO2020190192A1 - Warhead and method of producing same

Info

Publication number: WO2020190192A1
Application number: PCT/SE2020/050256
Authority: WO
Inventors: Christer Thuman; Björn Johansson; Hamzah HAMDAN
Original assignee: BAE Systems Bofors AB
Current assignee: BAE Systems Bofors AB
Priority date: 2019-03-19
Filing date: 2020-03-09
Publication date: 2020-09-24
Anticipated expiration: 2021-09-19
Also published as: SE1900053A1; CA3133776A1; EP3942248A4; JP7439120B2; US11953299B2; US20220155046A1; EP3942248A1; SE544060C2; JP2022525286A

Abstract

A procedure for producing a warhead (4) with controlled fragmentation comprising the step that an inner shell (1) is manufactured and filled with an explosive substance. The procedure further comprises the steps of providing a net (5) around 5 the outer surface of the inner shell (1) as well as depositing a material (8) on and around the net (5). A warhead is produced by the procedure and comprises an inner shell (1). A material (8) applied to the warhead (4) comprises weak points for guided fragmentation of the 0 deposited material (8) upon detonation of the warhead (4).

Description

WARHEAD AND METHOD OF PRODUCING SAME

TECHNICAL AREA:

The present invention concerns a procedure for producing a warhead with controlled fragmentation, whereby the procedure comprises the step that an inner shell is manufactured and filled with an explosive substance.

The invention also concerns a warhead produced by the procedure and comprising an inner shell.

OLDER TECHNOLOGY

Provision of preformed projectiles in warheads has been known for a long time. The effect is that with detonation the effectiveness as regards hard and soft targets varies depending on the spread upon detonation of projectiles with a preset size and mass. It is also possible to affect the direction in which the preformed projectiles will be spread.

Another way known to a person skilled in the art to produce projectiles with a predetermined size and mass is to effect controlled fragmentation of the warhead. In essence this means that weaknesses are provided in the warhead, for example by milling tracks in its material, so that at detonation the warhead divides according to these weaknesses rather than randomly.

It is also possible to combine the provision of preformed projectiles with controlled fragmentation in one and the same warhead.

A rubber fixture is often used during part of the manufacturing process to position preformed projectiles. Manufacture of the rubber fixture is in itself quite expensive and labor intensive. In a corresponding way, it is often difficult and work-intensive to produce guided fragmentation by milling tracks in the material of the warhead.

THE PROBLEM It is desirable to produce a simpler, faster, and more cost-effective method to manufacture a warhead with preformed projectiles and controlled fragmentation. SOLUTION TO THE PROBLEM

The objective of the invention is achieved when the procedure based on the invention is characterized in that it includes the following steps: a net is provided around the outer surface of the inner shell and a material is deposited on and around the net.

The objective regarding the warhead is reached if it is characterized by a material deposited on the warhead comprising weak spots for guided fragmentation of the deposited material upon detonation of the warhead. Further advantages are achieved if the invention also is given one or more of the characteristics in the dependent patent claims.

OVERVIEW OF THE DRAWINGS The invention will now be described with reference to the attached drawings. These show:

Fig 1 a perspective view of the inner shell of a warhead according to the invention;

Fig 2 a perspective view of the inner shell according to Fig 1, provided with a surrounding net;

Fig 3 a perspective view of a warhead with an outer layer of a deposited material;

Fig 4 a partially cut view of a warhead according to Fig 3; Fig 5 a view corresponding to the one in Fig 2 of a second embodiment of the invention;

Fig 6 a cut view of a section of the second embodiment of the warhead;

Fig 7 a perspective view of a partially assembled warhead according to the third embodiment of the invention; and

Fig 8 a view corresponding to the one in Fig 2 of a third embodiment of the invention.

PREFERRED EMBODIMENT

Fig la shows an inner shell of a warhead according to the invention; The inner shell 1 is hollow in order to enable provision of an explosive substance there. The inner shell 1 is also designed for receiving a nose part and a rear part at its front 2 respectively rear 3 end. The nose part and rear part can be given a number of embodiments depending on the desired characteristics of the warhead, but since they do not have to do with the present invention, they are not shown on the drawing figures. Part 6 in the middle is somewhat recessed in the embodiment shown, i.e. it has a somewhat smaller radius than the front 2 and rear 3 ends.

The inner shell 1 is preferably manufactured of some material judged by experts to be suitable for the purpose, most often a metallic material. A number of examples of materials are already known in the area. The present invention does not comprise manufacturing the material itself or the manufacturing method for inner shell 1. The invention functions independently of the choice of material and the manufacturing method of the inner shell.

A step in manufacturing a warhead 4 according to the invention is shown in Fig 2; A net 5 is provided around inner shell 1, preferably so that it encloses inner shell 1 in the circumferential direction. Net 5 extends along part of the inner shell 1 in the axial direction, but in the preferred embodiment the front end 2 and the back end 3 are left free for attachment to the nose resp. back parts. In the preferred embodiment net 5 is thus provided around recessed part 6.

In the embodiment shown, net 5 has square meshes 7, the size and form of which vary somewhat in the axial direction of the warhead in order to attach to the form of inner shell 1 with a radius that varies somewhat in the axial direction. The form of mesh 7 is variable within wide limits as is its size.

The manufactured material of net 5 is in many cases a metal that is selected so that it has characteristics that function together with a material applied to net 5. it will be described in further detail below. Some typical characteristics to consider with the choice of the material in net 5 are its melting point, its friability after heat treatment, and its ability to form alloys with other materials, especially material added later.

In certain embodiments net 5 has a retentive function for preformed projectiles provided inside the net. The size and form of the projectiles are variable. Some examples will be described below. Net 5 is designed so that it functions for intended retention of the projectiles, whereby the form and size of mesh 7 stops the projectiles from passing through them.

Fig 3 shows warhead 4 after a further manufacturing step. Laid-on material 8 has been applied on top of net 5 shown in Fig 2. The method of application varies, but a preferred embodiment is some form of additive manufacturing method. The material is applicable in powder form or in the form of threads and is melted in connection with the application so that it is immediately fixed at the intended place on warhead 4.

The choice between powder and thread in additive manufacture depends on, among other things, the geometric dimensions and the adhesiveness that is required of the finished product. Powder is often preferred with tight manufacturing tolerances, i.e. when the material that is added must reach spaces with small dimensions. Material in thread form is, however, generally more cost effective and is often viewed to be adequate for the relevant dimensions and requirements for strength. Material in thread form also has the manufacturing advantage that the amount of material which is unintentionally emitted to the environment is minimal, i.e. in principle, the process does not raise dust at all.

The high temperatures necessary for smelting the applied material 8 also means that the material in the underlying net 5 is affected. With a suitable choice of material, both of the material in net 5 as in the applied material 8, the material in net 5 melts, becomes brittle, or forms an alloy with the added material 8. An alternative is that net 5 and the added material 8 do not affect each other’s physical properties more than that the layer of added material 8 becomes thinner on top of the material added to net 5. In all of these cases, the added material and the temperature when adding the material are chosen so that the result is that the added material 8 and the net 5 form a unit together that includes weak spots where net 5 was originally placed.

The weak spots in the unit that is formed by the added material 8 and the net 5 will function to control fragmentation at the detonation of warhead 4. The part of the added material 8 which is arrayed in the mesh 7 of net 5 will thus form projectiles. This aspect of the preferred embodiment will be considered in the choice of added material 8 so that the projectiles formed have a suitable mass, and in the choice of the size and form of the mesh, so that the projectiles formed have a suitable size and form.

Some examples of material that can be chosen for the added material are aluminum, steel of various qualities, including stainless steel, and titanium, etc.

A partial cut through warhead 4 is shown in Fig 4, where both the net 5 and the added material 8 are visible.

Fig 5 shows a second embodiment of the invention. In this embodiment net 5 has considerably smaller mesh 7 than that shown in Fig 2 and Fig 4. A conceivable method of production of the net in Fig 5 is that holes of the desired size are made in sheet metal, for example by die cutting, etching, laser cutting, or with some other method of production that persons skilled in the art view as suitable. The net shown is especially suitable for retention of preformed projectiles with a cross section that is somewhat larger than the size of mesh 7. A cut view of inner shell 1, net 5, added material 8, and a large number of preformed projectiles 9 of warhead 4 is shown in Fig 6.

Arrangement of a number of preformed projectiles 9 in the warhead is accomplished with the help of a net 5 that is either a standard product or which can be

manufactured in a relatively simple and cost-effect manufacturing process. Net 5 does not need to be removed but remains an integrated part of warhead 4, which considerably simplifies the manufacturing process. Net 5 also contributes to controlled fragmentation of warhead 4 in a way that provides cost-effective production of warhead 4.

ALTERNATIVE EMBODIMENTS

An additional embodiment of a warhead 4 according to the invention is shown in Fig 7. The difference in relation to the embodiment that is shown in Fig 6 is that the preformed projectiles 9 that are arrayed outside inner shell 1 are in part larger and in part essentially square. Depending on the desired characteristics at detonation of warhead 4, this embodiment is interesting in certain applications, but it can naturally be varied further by a person skilled in the art.

Figure 8 shows warhead 4 according to Fig 7 with a net 5 provided on the outside of the preformed projectiles 9. It is clear that the mesh 7 of net 5 is smaller than the preformed projectiles 9 and will retain them before an external material 8 is laid on it.

The invention is thus variable in the framework of the attached patent claims. It can in particular be maintained that the invention comprises embodiments both with and without preformed projectiles 9. Net 5 constitutes controlled fragmentation such that it in many cases can be considered sufficient to constitute the desired effect of warhead 4. Embodiments with a combination of preformed projectiles 9 and controlled fragmentation are preferred in other cases.

Claims

PATENT CLAIMS

1. A procedure for producing a warhead (4) with controlled

fragmentation, whereby the procedure comprises the step that an inner shell (1) is manufactured and filled with an explosive substance characterized in that the procedure further comprises the steps:

- a net (5) provided around the outer surface of the inner shell (1);

- a material (8) applied in powder form or in thread form with an additive method of manufacture on and around the net (5);

2. A procedure according to claim 1, with steps characterized in that

- a number of preformed projectiles (9) are manufactured;

- the preformed projectiles (9) are arrayed along the outer surface of the inner shell (1), inside the net (5), so that the preformed projectiles (9) are retained in their respective positions;

- the material (8) is applied in powder form or in thread form with an additive method of manufacture on and around the preformed projectiles (9) at the same time as it is affixed on and around the net

(5);

3. A procedure according to claim 1 or claim 2, with steps characterized in that

- the material (8) which is applied in powder form or in thread form with an additive method of manufacture is applied with varying speed, so that weak points are produced in the material (8).

4. A procedure according to claims 1-3, with steps characterized in that

- the material (8) which is applied in powder form or in thread form with an additive method of manufacture is applied with varying temperature, so that weak points are produced in the material (8).

5. A warhead produced by a procedure according to any one of claims 1-4 and including an inner shell (1), characterized in that a material (8) applied to the warhead (4) comprises weak points for a guided fragmentation of the applied material (8) with detonation of the warhead (4).

6. A warhead (4) according to claim 5, characterized in that weak points in the applied material (8) are arranged in positions corresponding to the position of a net (5) that is provided outside the inner shell (1).

7. A warhead (4) according to claim 5 or claim 6, characterized in that

weak points in the applied material (8) are arranged in other positions that are selected by deposition of the material.

8. A warhead according to any one of claims 5-7, characterized in that a number of preformed fragments (9) are provided inside the applied material (8).